Stenting of the carotid artery (CA) is relatively new to interventional procedures. It is a challenging procedure because accessing the left or right carotid artery can be dependent on the anatomical disposition of the aortic arch.
FIG. 1 illustrates the aortic arch. As shown in FIG. 1, the aorta 1 includes an aortic arch region 3, a descending aorta 2, and an innominate 4. Three types of arches shown in FIG. 1: Type I, Type II and Type III arches. Also shown in FIG. 1 is the right subclavian artery (RSA) 5, left subclavian artery (LSA) 6, right common carotid artery (RCCA) 7 and left common carotid artery (LCCA) 8.
The arch types are defined by the height of the top of the aortic arch 3 from the base location where the innominate 4 attaches to the aorta. In a type I arch, the height is less than the diameter of the common carotid artery (CCA). Similarly, in a type II arch, the height of the top of the arch 3 from the base of the innominate 4 is of the order of 1 to 2 times the diameter of the CCA. In a type III arch, the height is more than twice the diameter of the CCA. As the height of the arch increases the procedures within the carotid arteries become more and more difficult due to the tortuous nature of the arterial connections to the aorta at the arch.
In type III hostile aortic arches, the angle of origin of the innominate artery or left common carotid artery can be very acute thus making the access of the left or right carotid arteries ostium difficult. This access is needed for endovascular stroke intervention for placement of stents as well as other intracranial arterial interventions, such as aneurysm repair. Subsequent placement of a stent delivery system or other interventional repair devices in a stable mode into the tortuous arterial system above it therefore becomes more difficult. The stenting and other interventional procedures itself are meant to re-establish a more normalized blood flow through the carotid and internal carotid artery into the brain by opening up regions of the artery constricted by plaque deposits which inhibit flow or by eliminating aneurysms that can burst and lead blood thereby starving the brain of oxygen.
The stents themselves can be self-expanding, balloon expandable, bio-absorbable, and/or covered. The stent delivery systems are designed to accommodate very acute bends but are reliant upon the guide catheter and guide wires and or embolic protection devices to stabilize them during deployment. Stents have been used to open “stenosis”— semi-occluded sections of the arterial system—for many years. They come in a wide variety and are designed for specific areas of the body, these include: balloon expandable, self-expanding, covered and bio-absorbable stents. Stenting in the neck and procedures above the neck are challenging when confronted with a type III hostile aorta, in particular stenting of the left or right carotid artery. During the insertion, manipulation and stabilization of the stent delivery mechanism and during removal of the guide wire and secondary wire, injuries to the subclavian artery and the tortuous aortic arch can happen. This can be caused by uncontrolled collapse of the sheath, embolic protection device (EPD) and stent/stent delivery system in the ascending aorta during procedure. This type of prolapse can result in the patient suffering cerebral embolism or stroke by dragging the fully deployed EPD over the carotid stenosis. Further, dragging the guide wires over the tortuous arterial regions can cause cutting into the arterial walls or otherwise injuring the artery resulting in dissections and trauma to the vessels involved. These traumas can be dangerous to the patient as they can ultimately directly affect blood flow by leakage at the dissections or by creating accumulation of thrombus, an organization of blood cells, which is a natural reaction to vessel injury. These may require additional procedures to repair and heal the damaged artery walls and prevent problems.
Similarly in the case of endovascular stroke interventions and other types of arterial interventions, such as aneurysm repair, some of the devices used are relatively stiff (e.g. the flow diverters used in wide necked aneurysm repair) and can push the sheath and device itself out of its location and the intracranial vascularity, creating major complications.
Even with the stabilization methods and systems described in the above-referenced co-pending patent applications, there is still the problem due to the need for stiff catheters and wires that are to be used to access the ostium of the tortuous vessels where treatment, such as stenting, has to be carried out. This is especially true in the case of acute type III aortic arches, which have to be navigated through, to access the carotid artery for above the neck procedures. Due to the tortuosity of the vessels originating from the aortic arch, the guiding catheter or sheath (even with a guidewire in place) can be unstable and as a result can “flip out” into the aortic arch during carotid stent delivery.